Stewart L. Udall, who as Interior secretary in the 1960s vastly expanded the country's system of national parks and monuments and developed far-reaching legislation to protect public lands, has died. He was 90.

FOR THE RECORD: Udall obituary: The obituary in Sunday's California section of former Interior Secretary Stewart Udall misidentified his father as Jesse Udall. His father was Levi Udall. —

FOR THE RECORD: Stewart Udall obituary: The obituary of former Interior Secretary Stewart Udall in the March 21 California section said that a few years ago he trekked with a grandson 7,000 feet up Bright Angel Trail, from the floor of the Grand Canyon to the South Rim. According to the National Park Service, the elevation change between the canyon floor and the South Rim is about 4,400 feet. —

Udall died Saturday morning at his home in Santa Fe, N.M., surrounded by his children, according to a statement from his son, Sen. Tom Udall of New Mexico. He died of natural causes after a fall last week that had kept him confined to bed.

Udall, who served in Congress and later led a crusade on behalf of victims of radiation exposure, had many accomplishments during his decades of public service. But his most important legacy came from championing the idea that government should preserve vast areas of land.

"Any wilderness area, any national park and national monument -- wherever you live in the United States now, there is one relatively close to you. He created the spirit that made all those things possible," said Carl Pope, chairman of the Sierra Club

"In 1960, most Americans lived thousands of miles from any national park," he said. "They don't anymore."

During the eight years that Udall served under presidents Kennedy and Johnson, he worked with the Sierra Club to create Redwood National Park along California's northern coast.

He also oversaw the creation of Guadalupe Mountains National Park in Texas, North Cascades National Park in Washington state and Canyonlands National Park in Utah, along with the Cape Cod National Seashore in Massachusetts and the Point Reyes National Seashore north of San Francisco.

He also helped write numerous pieces of legislation, including the Wilderness Act of 1964, which protects millions of acres.

"Many people at the time thought it was a crazy idea," he told the New York Times in 1989.

Stewart Lee Udall was born Jan. 31, 1920, in St. Johns, Ariz. He was one of five children raised on a small subsistence farm in the northeastern corner of the state, not far from Zuni and Navajo reservations.

His grandfather David King Udall founded the town after moving from Utah in 1880 as a Mormon missionary. Udall's father, Jesse, served as chief justice of the state Supreme Court.

Udall attended Thatcher Junior College and then the University of Arizona, pausing his studies to serve as a Mormon missionary in New York and Pennsylvania and as a B-24 tail gunner in Italy during World War II.

After the war, he returned to finish his degree and attend law school.

In 1954, Udall was elected to Congress and held the seat until President Kennedy tapped him to become secretary of the Interior. His brother Morris succeeded him in Congress. Morris' son Mark is a Democratic senator from Colorado.

Udall left government in 1969 and stayed in Washington for another decade practicing law and writing books.

He returned to Arizona in 1979 and pursued a lawsuit against the government on behalf of Navajo men who mined uranium and later developed cancer. The suit failed.

In 1994 Udall published a book that drew on that experience, "The Myths of August: A Personal Exploration of Our Tragic Cold War Affair with the Atom." In it he argued that leaders and scientists, intoxicated by the power of nuclear weapons, forged a secret national security state and that there was no military need for the United States to drop atomic bombs on Hiroshima and Nagasaki.

"Whether in the skies above Italy in World War II, in Congress or as secretary of the Interior, Stewart Udall left an indelible mark on this nation and inspired countless Americans who will continue his fight for clean air, clean water and to maintain our many natural treasures," President Obama said in a statement Saturday.

Udall, who counted poet Robert Frost and actor Robert Redford among his friends, was a committed outdoorsman.

During his years in Washington, he took his children to Interior Department outposts in the area on weekends and rafting down Western rivers in the summer.

A few years ago he trekked with a grandson 7,000 feet up Bright Angel Trail, from the floor of the Grand Canyon to the South Rim. He refused a National Park Service offer of a mule.

His family "wouldn't have liked it if I hadn't made it," he noted, "but what a way to go." Upon completing his ascent, he headed straight into the bar at the Tovar Lodge and ordered a martini.

Udall was married for 55 years to Erma Lee Udall. She died in 2001. He is survived by their six children and eight grandchildren.